Loans (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Investments in loans
Total gross loans	$ 5,187,475,000		$ 5,187,475,000		$ 4,754,788,000
Face value	5,283,932,000		5,283,932,000		4,845,115,000
Loan loss allowance (loans held-for-investment)	(4,342,000)	(2,816,000)	(4,342,000)	(2,816,000)	(3,984,000)
Carrying Value	5,183,133,000		5,183,133,000		4,750,804,000
Loans with variable rates of interest	3,877,333,000		3,877,333,000		3,231,334,000
Loans with variable rates of interest (as a percent)	74.80%		74.80%
Variable rate basis of loans			LIBOR
Weighted average spread of loans (as a percent)	5.65%		5.65%
Amount of loan impairment charges on individual loans held for investment			0		0
Allowance for loan losses as a percent of carrying amount			5.60%		5.60%
Activity in allowance for loan losses
Allowance for loan losses at the beginning of the period			3,984,000	2,061,000	2,061,000
Provision for loan losses			577,000	755,000
Recoveries			(219,000)
Allowance for loan losses at the end of the period	4,342,000	2,816,000	4,342,000	2,816,000	3,984,000
Recorded investment in loans related to the allowance for loan loss	289,470,000	160,893,000	289,470,000	160,893,000
Movement of loans held for investment
Balance at the beginning of the period			4,750,804,000	3,000,335,000	3,000,335,000
Acquisitions/origination/additional funding			1,860,026,000	1,308,602,000
Capitalized Interest			19,022,000	5,279,000
Basis of loans sold			(868,804,000)	(573,825,000)
Loan maturities/principal repayments			(633,425,000)	(140,596,000)
Discount accretion/premium amortization			10,147,000	14,243,000
Changes in fair value	11,608,000	458,000	32,501,000	458,000
Unrealized foreign currency remeasurement gain (loss)			16,462,000	(4,572,000)
Capitalized cost written off				(1,517,000)
Loan loss allowance, net			(358,000)	(755,000)
Transfer to other assets			(3,242,000)
Balance at the end of the period	5,183,133,000	3,607,652,000	5,183,133,000	3,607,652,000	4,750,804,000
1-month LIBOR
Investments in loans
Loans with variable rates of interest	137,092,000		137,092,000		150,076,000
Effective variable rate basis (as a percent)	0.1552%		0.1552%		0.1677%
3 Month LIBOR
Investments in loans
Loans with variable rates of interest	406,392,000		406,392,000		392,950,000
Effective variable rate basis (as a percent)	0.5525%		0.5525%		0.5233%
LIBOR floor
Investments in loans
Loans with variable rates of interest	3,333,849,000		3,333,849,000		2,688,308,000
Weighted average spread of loans (as a percent)	0.36%		0.36%		0.49%
LIBOR floor | Minimum
Investments in loans
Effective variable rate basis (as a percent)	0.15%		0.15%		0.19%
LIBOR floor | Maximum
Investments in loans
Effective variable rate basis (as a percent)	3.00%		3.00%		3.00%
Rating 2
Investments in loans
Total gross loans	429,357,000		429,357,000		364,491,000
Rating 3
Investments in loans
Total gross loans	4,309,365,000		4,309,365,000		3,905,204,000
Rating 4
Investments in loans
Total gross loans	289,470,000		289,470,000		265,640,000
Allowance for loan losses as a percent of carrying amount			1.50%
Rating 5
Investments in loans
Allowance for loan losses as a percent of carrying amount			5.00%
N/A
Investments in loans
Total gross loans	159,283,000		159,283,000		219,453,000
Total loans held-for-investment
Investments in loans
Total gross loans	4,890,196,000		4,890,196,000		4,367,702,000
Face value	4,987,325,000		4,987,325,000		4,455,533,000
Carrying Value of loan in default	4,400,000		4,400,000
Total loans held-for-investment | First Mortgages
Investments in loans
Total gross loans	3,259,428,000		3,259,428,000		2,714,512,000
Face value	3,317,358,000		3,317,358,000		2,766,217,000
Weighted Average Coupon (as a percent)			5.40%		5.50%
Weighted Average Life			3 years 10 months 24 days		4 years 3 months 18 days
Total loans held-for-investment | First Mortgages, excluding Cost Recovery Loans
Investments in loans
Total gross loans	3,255,012,000		3,255,012,000		2,701,731,000
Total loans held-for-investment | First Mortgages, excluding Cost Recovery Loans | Rating 2
Investments in loans
Total gross loans	101,875,000		101,875,000		94,981,000
Total loans held-for-investment | First Mortgages, excluding Cost Recovery Loans | Rating 3
Investments in loans
Total gross loans	3,010,516,000		3,010,516,000		2,452,763,000
Total loans held-for-investment | First Mortgages, excluding Cost Recovery Loans | Rating 4
Investments in loans
Total gross loans	142,166,000		142,166,000		153,987,000
Total loans held-for-investment | First Mortgages, excluding Cost Recovery Loans | N/A
Investments in loans
Total gross loans	455,000		455,000
Total loans held-for-investment | Subordinated mortgages
Investments in loans
Total gross loans	355,561,000		355,561,000		407,462,000
Face value	388,449,000		388,449,000		442,475,000
Weighted Average Coupon (as a percent)			8.60%		9.70%
Weighted Average Life			4 years 1 month 6 days		4 years 2 months 12 days
Total loans held-for-investment | Subordinated mortgages | Rating 2
Investments in loans
Total gross loans	104,821,000		104,821,000		103,369,000
Total loans held-for-investment | Subordinated mortgages | Rating 3
Investments in loans
Total gross loans	218,685,000		218,685,000		272,375,000
Total loans held-for-investment | Subordinated mortgages | Rating 4
Investments in loans
Total gross loans	32,055,000		32,055,000		31,718,000
Total loans held-for-investment | Mezzanine Loans
Investments in loans
Total gross loans	1,275,207,000		1,275,207,000		1,245,728,000
Face value	1,281,518,000		1,281,518,000		1,246,841,000
Weighted Average Coupon (as a percent)			10.60%		11.70%
Weighted Average Life			3 years 3 months 18 days		3 years 6 months
Total loans held-for-investment | Mezzanine Loans | Rating 2
Investments in loans
Total gross loans	209,690,000		209,690,000		153,119,000
Total loans held-for-investment | Mezzanine Loans | Rating 3
Investments in loans
Total gross loans	950,268,000		950,268,000		1,012,674,000
Total loans held-for-investment | Mezzanine Loans | Rating 4
Investments in loans
Total gross loans	115,249,000		115,249,000		79,935,000
Total loans held-for-investment | Cost Recovery Loans
Investments in loans
Total gross loans	4,416,000		4,416,000		12,781,000
Total loans held-for-investment | Cost Recovery Loans | N/A
Investments in loans
Total gross loans	4,416,000		4,416,000		12,781,000
Loans Held-for-sale
Investments in loans
Total gross loans	154,412,000		154,412,000		206,672,000
Face value	153,724,000		153,724,000		209,099,000
Weighted Average Coupon (as a percent)			4.70%		5.30%
Weighted Average Life			9 years 9 months 18 days		9 years 7 months 6 days
Loans Held-for-sale | N/A
Investments in loans
Total gross loans	154,412,000		154,412,000		206,672,000
Loans transferred as secured borrowings
Investments in loans
Total gross loans	142,867,000		142,867,000		180,414,000
Face value	142,883,000		142,883,000		180,483,000
Weighted Average Coupon (as a percent)			5.50%		5.40%
Weighted Average Life			2 years 9 months 18 days		2 years 10 months 24 days
Loans transferred as secured borrowings | Rating 2
Investments in loans
Total gross loans	12,971,000		12,971,000		13,022,000
Loans transferred as secured borrowings | Rating 3
Investments in loans
Total gross loans	$ 129,896,000		$ 129,896,000		$ 167,392,000